With the identification of prestin as the elusive lateral membrane motor protein of the outer hair cell (OHC), we are faced with the possibility of understanding how this single molecule can affect the mammal's exquisite sense of hearing. To that end, we have focused our interest on determining what protein structures may give rise to the motor's known biophysical attributes, including its temperature, tension, and voltage dependence. We hypothesize that these molecular activities arise and/or are influenced by interactions of prestin's intracellular C and N termini with other intracellular proteins and anions, and possibly by multimeric interactions, as well. We propose to target a focused set of aims, including 1) determine the contribution of prestin's C and N termini to prestin's signature biophysical attributes, 2) determine prestin's trafficking route in a prestin cell line that we have developed, and 3) determine what structures are different between prestin (slc26a5) and its closet family member slc26a6 that account for prestin's nonlinear capacitance. In order to reach these goals, we will employ a host of electrophysiological, molecular biological and biochemical methods. We believe that the information that we obtain through these studies will aid in understanding how the OHC enables us to hear so well and in turn how we might combat pathologies of the OHC that afflict millions.